fix(deps): upgrade pillow to 12.3.0 for security fixes

Resolves multiple high/medium severity Dependabot alerts: heap
out-of-bounds writes in ImageCmsTransform.apply(), Image.paste()/crop()
and ImageFilter.RankFilter, a JPEG2000 tiled-decode DoS, a decompression
bomb in PdfParser, a TGA RLE encoder heap data leak, an OS command
injection in WindowsViewer.get_command(), several decompression-bomb
check bypasses (GdImageFile, BdfFontFile, FontFile, PcfFontFile), an
out-of-bounds read via row stride on the mmap path, and an infinite
loop DoS in EpsImagePlugin.

GHSA-9hw9-ch79-4vh6, GHSA-vjc4-5qp5-m44j, GHSA-jjj6-mw9f-p565,
GHSA-6r8x-57c9-28j4, GHSA-fj7v-r99m-22gq, GHSA-xj96-63gp-2gmr,
GHSA-4x4j-2g7c-83w6, GHSA-phj9-mv4w-65pm, GHSA-45hq-cxwh-f6vc,
GHSA-5x94-69rx-g8h2, GHSA-8v84-f9pq-wr9x, GHSA-62p4-gmf7-7g93,
GHSA-pg7v-jwj7-p798

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: matrixise

requirements/dev.txt

@@ -140,7 +140,7 @@ packaging==26.2
     #   pip-audit
     #   pip-requirements-parser
     #   pipdeptree
-pillow==12.2.0
+pillow==12.3.0
     # via
     #   -c requirements/main.txt
     #   pillow-heif

requirements/main.txt

@@ -117,7 +117,7 @@ packaging==26.2
     # via gunicorn
 pandas==3.0.3
     # via -r requirements/main.in
-pillow==12.2.0
+pillow==12.3.0
     # via
     #   pillow-heif
     #   wagtail